In agricultural crop production, as a rule not only do the desired plants that have been planted on a field grow, but unwanted organisms, which may be wild or unwanted plants (also called weeds), fungi, or insects, also become established there. So as not to have to put up with overly large losses of yield due to the unwanted organisms, it is common practice to apply spray agents, in order to control the unwanted organisms. A field sprayer, which can be designed as a self-propelled or towed vehicle or as an attachment, is used for this.
For economic and environmental reasons, it is important to apply the spray only where it is in fact required. Two procedures are known in the prior art for selective application of spray.
On the one hand, there is the possibility of entering the location where unwanted organisms are found in an electronic map of the field. The map can be created in a survey of the field carried out before the spray operation, whether manually or by means of a sensor situated on a vehicle or aircraft (see, for example, U. Shapira et al., “Field spectroscopy for Weed Detection in Wheat and Chickpea Fields,” International Journal of Remote Sensing, 2013, Vol. 34, No. 17, pp. 6094-6108, or M. Koller et al., “Site-Specific Herbicide Applications Based on Weed Maps Provide Effective Control,” California Agriculture, Vol. 59, No. 3, pp. 182-187). Control of the nozzles of the field sprayer takes place automatically on the basis of the map and the current position of the sprayer.
On the other hand, there is also the possibility of outfitting the field sprayer or a vehicle towing or carrying it with a local sensor for unwanted organisms and to detect the organisms (online) while going over the field in order to control the nozzles of the sprayer in terms of an application of the spray to the unwanted organisms that were detected (see, for example, H. Böttger et al., “New Technology for Variable Spray Dispensing,” Landtechnik March 2003, pp. 142-143).
A control of the field sprayer based only on a map already produced some time ago (which, as proposed in the literature (M. Koller et al., op. cit.) can, for economic reasons, have been produced in the previous year or even before that) is subject to the disadvantage that the current distribution of the unwanted organisms in the field may no longer absolutely correspond with the map. Moreover, such maps, regardless of the chosen surveillance and logging technology, are not always of sufficiently high resolution and precise enough to reach all unwanted organisms with sufficient reliability and at the same time to waste as little spray as possible due to application of spray to unaffected places in the field.
The local sensor on the other hand suffers from the problem that the field sprayer needs to be moved over the field at a relatively high speed (on the order of magnitude of 10 km/h or higher) in order to keep operating costs at an economically acceptable range. However, the reaction times of the image processing system of the sensor and the valves of the nozzles are currently longer than the time that is actually available between the optical detection of the unwanted organisms by the sensor and the actual opening of the nozzle, and the time becomes even smaller if the sensors are not mounted on the front of the spray vehicle, as described in Böttger et al., but rather are mounted on the spray arm in order to avoid a second arm (see WO 2012/122988 A1). This has the consequence that distances on the order of magnitude of about 10 m cannot be sprayed.
Thus, there is a need for making available a method and a device for controlling unwanted organisms on a field and a corresponding machine to overcome the aforementioned disadvantages in the art.